Anode Composition Comprising Acrylonitrile-Acrylic Acid Copolymer As Binder, Method For Preparing The Anode Composition And Lithium Secondary Battery Using The Anode Composition

Abstract

An anode composition for a lithium secondary battery is provided. The anode composition comprises an anode active material, a conductive material, and an acrylonitrile-acrylic acid copolymer with a high molecular weight as a binder. The acrylonitrile-acrylic acid copolymer has a molar ratio of acrylonitrile to acrylic acid of 1:0.01-2. Further provided are a method for preparing the anode composition and a lithium secondary battery using the anode composition. The binder has improved resistance to an electrolyte solution due to its enhanced adhesive strength. In addition, the use of the anode composition prevents the active material layer from being peeled off or separated from a current collector during charge and discharge to achieve improved capacity and cycle life characteristics of the battery.

Description

TECHNICAL FIELDThe present invention relates to an anode composition comprising an acrylonitrile-acrylic acid copolymer with a high molecular weight as a binder, a method for preparing the anode composition, and a lithium secondary battery using the anode composition. The binder has improved resistance to an electrolyte solution due to its enhanced adhesive strength. In addition, the use of the anode composition prevents the active material layer from being peeled off or separated from a current collector during charge and discharge to achieve improved capacity and cycle life characteristics of the battery.BACKGROUND ARTWith recent technological advances and increasing demand for mobile devices, there has been dramatically increased demand for secondary batteries as energy sources. Particularly, lithium secondary batteries are widely used at present for their high energy density and high voltage. A typical lithium secondary battery uses a lithium transition metal oxide as a cathode ...

AI Technical Summary

Benefits of technology

The present inventors have earnestly and intensively conducted research to solve the above problems. As a result, the present inventors have found that the use of a particular acrylonitrile-acrylic acid copolymer as a binder in the preparation of an anode composition for a lithium secondary battery resulted in enhanced adhesive strength and improved electrolyte solution resistance of the anode composition.

According to the present invention, the use of the acrylonitrile-acrylic acid copolymer with a high molecular weight as a binder for an anode improves the adhesion of the electrode composition to a current collector and reduces dissolution or swelling of the electrode in an organic electrolyte solution to prevent the active material from being peeled off or separated from the current collector despite repeated charge and discharge. Therefore, a lithium secondary battery comprising an anode produced using the binder can be effectively inhibited from reduction in capacity and output retention.

Problems solved by technology

However, lithium suffers from the disadvantages of unsafety and poor cycle characteristics due to dendrite growth during repeated charge / discharge cycles, thus being unsuitable for use in secondary batteries.

Although extensive research has been conducted on the use of lithium in the fabrication of secondary batteries, many problems still remain unsolved.

However, an anode made of a carbon-based material has a theoretical maximum capacity of 372 mAh / g (844 mAh / cc) and thus has a limitation in capacity increase.

This limitation makes it impossible for the anode to perform a sufficient role as an energy source of next-generation mobile devices that are rapidly being developed.

Due to this volume change, the anode active materials are separated from current collectors or the anode active material particles are broken into smaller pieces during continued charge and discharge, causing a loss in electrical contact.

Further, the irreversible discharge capacity close to 50% of the initial capacity results in a marked reduction in capacity as the charge / discharge cycles proceed, leading to poor cycle life characteristics.

This volume variation leads to a degradation in the performance (e.g., shortened cycle life) of a battery using the anode active material.

The use of a binder in an excessively large amount for the purpose of reducing a change in the volume of an active material during charge and discharge can somewhat prevent the separation of the active material from a current collector, as mentioned above, but involves many problems, for example, an increase in the electrical resistance of an anode due to the electrical insulating properties of the binder and a decrease in the capacity of a battery due to the relatively small amount of the active material.